Hydraulic positioning apparatus



March 29, 1966 M VENNER ET AL 3,242,821

HYDRAULIC G PO'S ITINING APPARATUS Filed July 22, 1964 fW/f VENT

INVENTORS M/CHEL' VEN/VER X BiO/VAL!) WLTERS United States Patent O 3,242,821 HYDRAULIC POSITIONING APPARATUS Michael Venner, London, and Ronald Walters, Wembley, Middlesex, England, assignors to The Sperry Gyroscope Company Limited, Brentford, England, a company of Great Britain Filed July 22, 1964, Ser. No. 384,484 Claims priority, application Great Britain, July 26, 1963, 29,649/ 63 5 Claims. (Cl. 91167) The invention relates to hydraulic positioning apparatus tor use, for example, for positioning a load such as the worktable of la drilling machine in any one ot a number of predetermined positions.

An object of the invention is to provide apparatus ot this kind which can be arranged .to Irespond to signals in binary coded form, and to provide hydraulic jack units for use in such apparatus.

According to one aspect of the present invention a telescopic jack unit comprises a set of hydraulic jacks arranged one within the other, the cylinder of each, except the outermost, heing formed in a sleeve which provides part ot the piston of the next outer jack orf the set, the jacks being provided with ports for independent operation, and being arranged to produce relative movements of the extreme members of the set which are proportional to terms of a binary power series.

Preferably, each piston is provided with two piston surfaces, one of which is arranged so that in ope-ration it is exposed to hydraulic tiuid at the full supply pressure, while the second is of approximately twice the area of the first and is exposed to hydraulic fluid in `a chamber which may be connected in operation either directly to the sup ply, or exhausted to a tank. The invention includes hydraulic positioning apparatus including one or Imore telescopic jack units of the kind described in combination with valves for controlling the pressures applied to the piston to actuate the jacks, and the valves may he electrohydraulic valves and may be mounted directly on the body of the jack unit.

To provide positioning apparatus with la sutiicient range of positions, two or more units of the kind described may be coupled together so that the displacements produced by the individual jacks are additive, and are proportional to consecutive terms of a binary power series.

'Phe invention will be further described )by IWay oct example with reference to the accompanying drawing which represents diagrammatically a longitudinal section through a hydraulic positioning device laiccording to the invention.

rllhe device consists of two telescopic jack units coupled together hy sharing ya common outermost body, and arranged to extend or withdraw ya pair of end members which constitute the innermost pistons of the sets of jacks of the two units 'through la range of sixtytour positions spaced at 0.1 inch apart over a distance of 6.3 inches in response to a signal representing the six digits of a binary coded number. One set of jacks has its piston with individual movements ot 3.2 inches, 0.2 inch and 0.1 inch while the other pistons with movements of 1.6 inches, 0.8 inch and 0.4 inch.

The device comprises a cylindrical outer hody l1 trom which extend the end members 2 and 3 which Vare the innermost piston rods of the two sets of telescopic jacks.

The end member 2 carries 'a piston head 4 working in a cylinder formed in la sleeve 5. The outer end off this cylinder communicates through passageways with a port 6 on the outside ot the jack 'body 1 which may be connected either to the hydraulic supply at high pressure, x, or exhausted to the tank, t, under the control of a solenoid valve 6 which ymay Ibe actuated Iby Ian electrical signal s.

The other side of the piston head 4 carries an extension ICC piston rod 7 terminating in 'a further piston head 8 within a charnher 9 arranged to he connected to the supply of hydraulic fluid 4at high pressure through :a port 10 in the jack body. The Iarea of the piston head 8 exposed to the hydraulic iluid in the chamber 9 is half of the annular area of the piston head 4 exposed to the hydraulic duid Within the cylinder 5. The space between the piston heads 4 and I8 surrounding the rod 7 is vented to the tank through a port 11 in the side of the jack body.

The sleeve 5 which dorms the cylinder for the piston head 4 is itself formed at its outer or lett end, las viewed in the drawing, with a piston head 12 working within a sleeve 13 tforming a cylinder for it.

The other end of the sleeve 5 is joined .to a further sleeve 14 extending into the chamber 9 where it forms effectively a further piston head and also acts as a cylinder for the inner piston head 8.

The end of the cylinder in the sleeve 13 beyond (to the left of) the piston head 12 is connected Ithrough a por-t 15 in the jack hody to a solenoid-operated valve :15' by means of which it rn-ay either be put into communication with the high pressure supply of hydraulic fiiuid, or may be vented yto the tank. The `annu-lar area on the piston head 12 is twice the 'annular area of the end of the sleeve 14 exposed to the hydraulic fluid in the chamber 9. The space between these two piston heads is vented to the tank through the port 11.

The sleeve 13 itself forms va piston, in turn Abeing provided With la piston head 16 working within the jack body 1 and connected to a solenoid Ivalve 17 through a port 17. The other end of the sleeve 13 is connected to Ia turther sleeve 18 Iwhich forms a cylinder within which -a portion of the sleeve 14 lacts as ya piston Iand which also serves as a piston exposed to the fluid in .the chamber 9. The annular area of this piston is half of the annular area of the piston head 16. lThe spiace between the two piston heads is vented to the tank through the port `11.

The design of the piston heads and the cylinders is such that they have stop surfaces .accurately machined so that the travel of the innermost piston head 4 is 3.2 inches, the travel of the piston head L2 is 0.2 inch, and the travel ot the piston head 16 is 0.1 inch.

The other portion of the jack Iassembly within the tbody 1 is of ya further set of three telescopic jacks, the innermost member of which is constituted by a piston rod 3 and which are similarly .operated by connecting ports l19, 20 Iand 21 to the high pressure supply or to the tank by means of solenoid-operated valves 19', 20 and 21', respectively.

The construction of this set of jacks is closely similar to the set just described, each having double piston suriiaces, one set of which is exposed to pressure applied through the ports 19, 20, or 21 while the other, in each case of half of the area of the corresponding piston off the tirst set, is exposed to the pressure of the supply in the chamber 9. The travels of the jacks of the right hand set are, 'from the innermost outwards, 1.6 inches, 0.8 inch and 0.4 inch.

In operation, the chamber 9 is connected to a supply of hydraulic -fluid at high pressure through -the port 10 and the ports 6, 15, 17, 19, 20 land 21 are connected through their respective solenoid-operated valves 6', 15', 17,19', 20 and 21' alternatively to this supply or to fthe tank.

When all the solenoid valves are operated to connect their respective ports to the high pressure supply the device is in i-ts retracted position since the outer pistons in each case heing twice the area of the inner pistons the hydraulic pressure is effective to move all pistons to Itheir innermost positions.

By connecting any port to the tank, the pressure in the chamber 9 causes the respective piston to be mowed to its outer position, and the device to :be extended by an amount corresponding to the travel of this piston. For example, if the ports 15, 17 and 19 yare connected to the supply and ports 6, 20, 21 to the tank the device is extended through a distance of 4.4 inches from its fully retracted position.

lf the high speed of ope-ration is of great importance it is desirable that the pistons with the greatest length of travel should ybe the innermost pistons of the telescopic assembly, as is the case in the embodiment described.

The electro-hydraulic valves may Ibe mounted directly on the body of the unit.

The arrangement described could be inverted if desired, the jack bodies forming the end members of the system. Alternatively, two or more jack assemblies or devices according to the description above could be combined by connecting one end member of one to an end member of the second.

In apparatus of thigh accuracy it may be desirable to compensate 'for changes in length due to 'change of tcmperature of the apparatus. This may be drone wholly or in part by supporting one .of the end members from a framework consisting of tubing lthrough which the 'hydraulic fluid is caused `to circulate. By this means the framework is brought to `the same temperature as the jack assemblies. If the framework is made of tubing of higher co-eicient of thermal expansion `and off proportionately shorter length, correction of thermal expansion may be achieved.

What is claimed is:

1. A digital 4actuator comprising (a) a housing having a cylindrical bore therein,

(b) a set of hydraulic jacks arranged one within the other in telescopic fashion,

(l) the cylinder part of each of the jacks forming the piston part of lthe next outer jack,`

(2) the cylinder of the outermost jack forming a piston part within -said housing bore,

(3) each of the piston parts having two piston surfaces one substantially greater than the other, and

(4) each of the jacks of the set being so relatively laxially dimensioned that the relative Iaxial movements thereof between `the innermost piston and Athe housing are proportional to predetermined terms -of a binary power series,

(fc) port means in said housing communicating with ltJhe smaller surfaces of each of said piston part-s and adapted to supply thereto hydraulic fluid under a substantially constant lsupply pressure, and

(d) further port means in said 4housing communicating with the larger surfaces of each of said piston parts and adapted selectively to supply hydraulic lluid thereto at said sup-ply pressure or to .remove hydraulic 4fluid pressure ltherefrom depending upon a given value of the terms of said binary series.

2. The digital actuator `as set forth in claim 1 wherein said pio-rt means includes .a chamber in said housing and wherein the smaller surfaces of said piston parts form one wall portion of said chamber.

3. The digital actuator -as set forth in claim 1 wherein said housing includes ya second cylindrical bore and a second set of :hydraulic jacks arranged therein identically with said rst set )but wherein each of said se'oond set of jacks is so relatively axially dimensioned as to pirovide axial movements thereof between the innermost piston and said housing proportional to further predetermined terms of a binary power series.

4. The ldigital actuator as set forth in claim 3 wherein said ports means includes a chamber in said housing comm-on to each set of jacks and wherein eac-h of fthe smaller surfaces of the piston parts of each set lform wall portions of said chamber.

5. 'Ilhe digital lactuator as set forth in claim 4 wherein said cylindrical housing lboeres are coaxial and wherein said common :chamber is arranged .between said sets of jacks with `the smaller surfaces of the piston parts thereof forming opposing wall portions of said chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,630,786 3/1953 Poore 92-52 2,831,464 4/ 1958 Lillquist 92-52 3,141,388 7/1965 Brandsteder 91-167 X SAMUEL LEVINE, Primary Examiner'.

P. T. COBRIN, Assistant Examiner. 

1. A DIGITAL ACUATOR COMPRISING (A) A HOUSING HAVING A CYLINDRICAL BORE THEREIN, (B) A SET OF HYDRAULIC JACKS ARRANGED ONE WITHIN THE OTHER IN TELESCOPIC FASHION, (1) THE CYLINDER PART OF EACH OF THE JACKS FORMING THE PISTON PART OF THE NEXT OUTER JACK, (2) THE CYLINDER OF THE OUTERMOST JACK FORMING A PISTON PART WITHIN SAID HOUSING BORE, (3) EACH OF THE PISTON PARTS HAVING TWO PISTON SURFACES ONE SUBSTANTIALLY GREATER THAN THE OTHER, AND (4) EACH OF THE JACKS OF THE SET BEING SO RELATIVELY AXIALLY DIMENSIONED THAT THE RELATIVE AXIAL MOVEMENTS THEREOF BETWEEN THE INNERMOST PISTON AND THE HOUSING ARE PROPORTIONAL TO PREDETERMINED TERMS OF A BINARY POWER SERIES, (C) PORT MEANS IN SAID HOUSING COMMUNICATING WITH THE SMALLER SURFACES OF EACH OF SAID PISTON PARTS AND ADAPTED TO SUPPLY THERETO HYDRAULIC FLUID UNDER A SUBSTANTIALLY CONSTANT SUPPLY PRESSURE, AND (D) FURTHER PORT MEANS IN SAID HOUSING COMMUNICATING WITH THE LARGER SURFACES OF EACH OF SAID PISTON PARTS AND ADAPTED SELECTIVELY TO SUPPLY HYDRAULIC FLUID THERETO AT SAID SUPPLY PRESSURE OR TO REMOVE HYDRAULIC FLUID PRESSURE THEREFROM DEPENDING UPON A GIVEN VALUE OF THE TERMS OF SAID BINARY SERIES. 